This invention is related to clamping latches rigidly mounted on a supporting member and pivotal into and out of engagement with a work-piece in a high temperature environment contaminated by very small particulate debris. More specifically the present invention is related to a latch for clamping a semiconductor wafer to a support ring during processing including plasma vapor deposition and sputtering.
Typically, semiconductor wafers are detachably mounted to a ring support member during processing. A plurality of latches mounted proximal to the periphery of the ring support member resiliently bias the wafer against a portion of the ring more distal there from.
Each latch is provided with a first freely rotating engagement member extending radially inwardly from the point of engagement of the latch with the ring for resilient and rolling engagement with a peripheral portion of the wafer. The latch is also provided with a second freely rotating engagement member extending radially outwardly from the point of engagement of the latch with the ring for resilient and rolling engagement with a peripheral portion of the ring support member.
The latch is pivotally secured to the ring support member for rotation about an axis normal to the axis of rotation of the first and second rotating engagement members. Pivoting the latch moves the second rotating engagement member into and out of engagement with the wafer. Unintended pivotal movement of the latch is resisted by engagement of the second rotating engagement member with a well or depression in the peripheral surface of the ring when the first rotating engagement member is not engaged to the wafer. When the second rotating engagement member is engaged to the wafer, a depression or concavity in the ring member secures the latch against unintended pivotal movement but also provided for resilient biasing of the latch against the wafer.
The most recent prior art includes such latches as shown in U.S. Pat. No. 6,299,153 issued to the inventors of the present invention on Oct. 9, 2001 and U.S. Pat. No. 6,143,147 issued to Vaclav Jalinek on Nov. 7, 2000.
The inventors of the present invention found that the first and second engagement members of the latch shown in U.S. Pat. No. 6,143,147 experienced binding due to work wear and other work conditions. Such binding of the second engagement members resulted in surface damage to the wafer when the latch was pivotally rotated from an engagement to disengagement position or visa-versa. Moreover, binding of the first engagement member resulted in excessive resistant and even failure of the latch to properly pivot. In their U.S. Pat. No. 6,299,153, the inventors of the present invention called for the use of ball bearings on one or more of the first engagement member, second engagement member and the pivotal attachment of the latch to the ring.
The ball bearing design shown in U.S. Pat. No. 6,143,147 has experienced failure including binding of the ball bearings and fracture of the latch body engaged to the ball bearings. The present invention is directed to a novel design of the latch body and ball bearing mechanism providing pivotal movement of the latch on the ring support.
It is among the objects and advantages of the invention shown and claimed herein
to provide a latch and ball bearing assembly which includes a fail-safe feature to prevent binding of the pivotal movement of the latch.
It is a further object and advantage of the present invention to provide a latch and ball bearing assembly which will not suffer from fracture at the point of engagement of the balls of the bearing with the latch.
It is yet another object and advantage of the present invention to provide a latch assembly in which the ball bearing assembly providing pivotal movement for the latch may be quickly and easily removed and replaced as a unit.
It is still another object and advantage of the present invention to provide a latch and ball bearing assembly in which the balls of the ball bearing do not engage the latch body eliminating the requirement for tight tolerances between the balls and the body of the latch and the need for a tungsten carbide retaining washer required in the prior art assembly.
These objects and advantages as well as other objects and advantages may be achieved by the latch claimed herein, one embodiment of which is described and shown in the specification and drawings.
A latch for releasably holding a semiconductor wafer to wafer supporting means including means for rotatably mounting a latch body on wafer supporting means, said means including, a ball bearing having an inner race and an outer race, the inner race being rotatably on the mounting means, the outer race being rotatably if the inner race becomes non-rotatable, resilient means between the ball bearing and the latch body normally biasing the ball bearing away from the latch body, and first retainer means on the mounting means for preventing the separation of the ball bearing from the mounting means and second retainer means on the mounting means for preventing the latch body from separating from the mounting means.